The field of the invention is fluid catalytic cracking (FCC).
FCC technology, now more than 70 years old, has undergone continuous improvement and remains the predominant source of gasoline production in many refineries. This gasoline, as well as lighter products, is formed as the result of cracking heavier, less valuable hydrocarbon feed stocks such as gas oil.
In its most general form, the FCC process comprises a reactor that is closely coupled with a regenerator, followed by downstream hydrocarbon product separation. Hydrocarbon feed contacts catalyst in the reactor to crack the hydrocarbons down to smaller molecular weight products. During this process, coke tends to accumulate on the catalyst which is burned off in the regenerator.
When an atmospheric residue or a vacuum residue feed is to be cracked via FCC, with either propylene or gasoline as the desired product, light cycle oil (LCO), a less desireable product is also produced and can be directed to the diesel pool. LCO is a highly aromatic product boiling in the diesel range (300-700° F.). Due to its aromatic nature, LCO has a very low cetane number in the range of about 20 to about 25 and has limited applicability as a blendstock for diesel fuel without extensive hydrotreating. Additionally, it is resistant to cracking in the FCC process due to its aromatic nature. Accordingly, LCO may degrade the quality of the diesel pool due to its high aromaticity and low cetane value. Upgrading of LCO to petrochemicals would be desirable.
Heavy Cycle Oil (HCO) is also produced in the FCC unit with little use other than for fuel oil. Further conversion of the HCO to motor fuel products would also be desirable.
Also, clarified slurry oil, (CSO), a heavy oil is also produced as a byproduct of catalytic cracking. These are highly aromatic, high boiling, dense liquids and are the hydrocarbon fractions which remain as a bottoms fraction after catalytic cracking and are used primarily as heavy fuel oil. Further conversion of the CSO to motor fuel products would also be desirable.